The OPERA Spectrometer Slow Control System

OPERA is a long-baseline neutrino experiment at the Gran Sasso underground laboratories (LNGS), designed to observe nu - tau appearance in a nu - mu neutrino beam shot from CERN. The detector has a modular structure and is composed of two identical supermodules, each consisting of a massive lead/nuclear emulsion target complemented by electronic detectors and a magnetic spectrometer. The two magnets are instrumented with around 1000 resistive plate chambers (RPCs) detectors covering a surface of about 3200 m2. The slow-control system has been designed to monitor and control all the critical parameters for a proper functioning of the spectrometer. The different hardware (high voltage power supplies, RPC current meters, RPC and magnet temperature sensors, timing boards) is read out via CANbus connections by several distributed clients. The clients write the data to a relational database (PostresSQL), which is the heart of the system: it gives persistency to the data and allows to perform correlations useful to debug possible system malfunctioning. Among the various tools (histogramming and XML configuration managers), a controller process checks for possible failures of the system using data from the database and generates warnings/alarms for the shifters.